Simulation network



Aug- 17, 1965 R. w. DE MONTE 3,2o1,719

SIMULATION NETWORK Filed 001;. 20, 1961 /NVENTOR By R. W DE MONTE wym TTORNEV United States Patent O 3301:7197 EMUA'HN flETV/'fdl Robert De Monte, Eerlreiey Heights, NJ., assgner to Eel 'felephone Laboratories, fncorporated, New York, FLY., a eorporaticn of New York Fiied Get. 2h, 1961, der. No. 1525531 6 Ciainis. (Ci. 333-232) This invention relates to wave transmission networks and more particularly to simulation networks or artificial lines.

The object of the invention is to simulate the image admittance and propagation of a section of transmission line within a sheath, such as a Cable. Related objects are to increase the accuracy, widen the band, simplify the structure, and reduce the cost and size of such a simulation network.

Cables comprising a number of pairs of insulated conductors surrounded by a conductive sheath find extensive use in wave transmission systems. The sheath is generally grounded or otherwise fixed in potential. lt is often desirable to have a network which 'will accurately simalate both the image admittance and the propagation of a section of such a conductor pair within a sheath or cable. Simulation networks of this type are extensively used in planning new communication systems and in testing component apparatus under simulated Operating conditions.

The network in accordance with the present invention closely simulates a section of tWo-conductor transmission line within a sheath over a wide band of freqnencies. In practice, simulation within half a percent in the resistance and the reactance of the image admittance and in the real and the imaginary parts of the propagation constant have been attained over a frequency range of 50 to 10,000 cycles per second. For this accuracy, the structure requires the minimum number of component elements, thns reducing the cost and size.

The network is in the form of a symmetrical lattice with two capacitive shunt branches connected at the respective ends thereof. The capacitance of each of these shunt branches is equal to half of the distributed capacitance between the conductors and the sheath of the line section to be simulated. The admittances of the series and diagonal branches of the lattice are evaluated in terms of the image admittance and the propagation constant of the line section at a selected frequency to provide effect smulation at this frequency. With proper realization of these admittances, excellent simulation is obtained over a wide range of frequencies extending on both sides of the selected frequency. In the specific embodiment shown, each series branch of the lattice comprises a resistor equal in value to one-half of the directcurrent resistance of the two conductors of the line section connected in series. Each diagonal branch comprises the series combination of a resistor and a capacitor. For the longer line Sections, each series branch may include aiso a series inductor.

The nature of the invention and its various objects, features, and advantages will appear more fully in the following detailed description of the typical embodiments illustrated in the accompanying drawing, in which:

PIG. 1 is the schematic circuit of a lattice network used in explaining the invention;

PIG. 2 is a generalized schematic circuit of a Simulation network in accordance With the present invention; and

PIG. 3 is a schematic Circuit of one embodiment of the network shown in FG. 2.

The symmetcal lattice shown in FIG. 1 comprises two equal series admittances YA, YA and two equal diagonal admittances Y YB connected between a pair of input terminals t-ff and a pair of output terminals E2- JCC 13. It is known that such a network Will simulate exactly the image admittance YI and the propagation of a uniform section of transmission line at all frequencles if YA=Y1 cot hl; (1)

and

YB=Y1 tan h; (2) Where P is the propagation Constant of the section.

The network in accordance with the invention shown in FIG. 2 is the exact equivalent of the lattice of PIG. 1 at a selected radian frequency wo. In FG. 2, two end shunt capacitors, each of value 00/2, have been added. Also, the admittances provided by these capacitors at wg have been subtracted from the branches of the lattice. Thus, at wg, each modified series admittance is given by YAI=Y1 (30h L-C0w02 and each modified diagonal admittance is given by YBI-:YI 'ln Cowfz where P is the propagation Constant of the line section at wn. When the capa-citance C0 is made equal to the distributed lcapacitanee between the pair of conductors and the sheath of the section, the network 'of |PIG. 2 will give excellent sirnulation not only at wo but over a wide range on either side of wo. In practice, wo is generally chosen somew'hat above the middle of the desired Operating range.

PIG. 3 shows a more specific embodiment of the net- Work of FIG. 2. ln FIG. 3, each end shunt capacitance is furnished by two equal, series-connected capacitors each yof value C0, With a common termin-al 14 which may be grounded to provide a balanced-to-ground structure. Each series branch comprises a resistor R1 equal in value to onehalf of the direct-current resistance of the two conductors of the line section connected in series. Each diagonal branch comprises a resistor of value R2 and a capacitor of value C2 in series. The values of R2 .and C2 are chosen to provide the 'required admittance YB', at wo. Therefore R2 in ohms is equal to the real part of and C2 in far-ads is equal to the imaginary part of 1 an Y, est lig-00m2) As -an example, a network to simulate 3000 feet of 22- gauge telephone cable Will now be presented. In this cable, the direct-current resistance is 173 -ohms per mile and, at wg,

P=0.473+j0.567 in nepers and radians per mile and YI=3216+j2657 micromhos e,ao1,719

The component elements will have the following values:

C=0.025 62 microfarad C2=0.01047 microfarad L1'= 128 m-icrohenries R1=49.15 ohms R2=1017 ohms It is to be understood that the above-described arrangernents are only illustrative of the application of the prinlciples of the invention. Numerous other arrangements may be devised by those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

1, A network for simulating the image admittance Y; and the propagation of a section of transmission'line in the form of a pair of conductors with a surrounding sheath comprising a lattice and twol capacitive shunt branches Vconnected to the respective ends thereof, the capacitance at a selected radian frequency wo within the Operating range, where P is the propagation .constant of the line section at wo.

2. A network in accord-ance with claim 1 in whic-h each shunt branch includes two series-connected capacitors each of value C0 `and a terminall common to the capacitors.

3. A network in acoordance With claim 1 in which each diagon'al branch comprises the series combination of a resistor and 'a capacitor. w

4. A network vfor simnlating a section of two-eonductor transmisson line within a sheath comprising a symmetrical lattice and two shunt 'branches connected at 'the respective ends thereof, each series branch of the lattice comprising a resistor equal in Value to one-half of the direct-current resistance of the two conductors of the line section con- 'nected in series, each diagonal branch of the lattice comprising the series combination of a resistor of Vvalue` R2 and a capacitor of value C2, 'and each of the shunt branohes including a :capacitance equal to half of the distributed capacitance C0 between the conductors and the sheath of the line section, where R2 is equal to the real par-t of 1 YI ten' h-coe/z C2 is equal to the imaginary part of YI hall ;L- Cnwg/ n1ission line surronnded by a conductive sheath comprising a lattice and two capacitive shunt branches connected at the respective ends thereof, each 'shunt branch having a capacitance equal to half of the distributed capacitance C0 between the conductors 'and the sheath of the line section -to be simulated, each series branch of the lattice comprising the `series combination of a resistor of value 'R1 .and an inductor of value L1, the admittance of each diagonal branch of the lattice being equal to i `YI tan h-cowq/a at a selected radian frequency wo within the Operating range, where P is the propagation constant of the line section at wo, R1 lis equal to Vone-half of the direct-current resistance of the two condnctors -of the line section connected in series, and L1 is equal to the limaginary part of 6. A network for simulating the image admittance YI and the propagation of a section of transmission line in the form of two conductors and a surrounding sheath comprising a lattice and two capacitive shunt branches connected one atV each end of the lattice, each shnnt branch having a oapacitance equal to 'half of the distributed -capacitance C0 between the two conductors and the' sheath of thel line section to be sirnulated, each series branch of the lattice comprising the series combination of a resistor of value R1 and an indnctor, of value L1, and each diagonal branch 'of the lattice comprising the series combination of a resistor of value R2 and a capacitor of value C2,

where R1 is equal to one-half of the direct-current resist- Aance of the two conductors of the line section, connected in series L1 is equal to the imaginary part of R2 is equal to the real part C2 is equal to the imaginary part of YI tan hIV-Cowo/ 'P is the propagation constant of the line section at wo, and wo is a selected radian frequency within the Operating 2 range.

References Cited byvthe Examiner f UNITED STATES PATENTS i I 1,64?,332V -9/27 Campbell 333-23 ?1,767,'199 6/30 Bartlett '333-23 1,7=8\8,526 1/31 Johnson 3334-23 1,799,'7*94 4/ 3 1, Horton 333-423 1,958,742 5/34 C'auer 333-23 2,1'8-3,l23 '12/39 Mason i 333- 2,965,=8459 12/60 De Monte 333-74 HERMAN KARL SAALBACH, Primary Examz'ner. 

1. A NETWORK FOR SIMULATING THE IMAGE ADMITTANCE Y1 AND THE PROPAGATION OF A SECTION OF TRANSMISSION LINE IN THE FORM OF A PAIR OF CONDUCTORS WITH A SURROUNDING SHEATH COMPRISING A LITTICE AND TWO CAPACITIVE SHUNT BRANCHES CONNECTED TO THE RESPECTIVE ENDS THEREOF, THE CAPACITANCE OF EACH SHUNT BRANCH BEING EQUAL TO HALF OF THE DISTRIBUTED CAPACITANCE C0 BETWEEN THE CONDUCTORS AND THE SHEATH OF THE LINE SECTION, EACH SERIES BRANCH OF THE LATTICE COMPRISING A RESISTOR EQUAL IN VALUE TO ONE-HALF OF THE DIRECTCURRENT RESISTANCE OF THE TWO CONDUCTORS OF THE LINE SECTION CONNECTED IN SERIES, AND THE ADMITTANCE OF EACH DIAGONAL BRANCH OF THE LATTICE BEING EQUAL TO 